FLOWERING TRUNKS. 35 



of on the upper part of the tree. The cacao-tree is a 

 well-known example of this peculiarity, which is not 

 uncommon in tropical forests ; and some of the smaller 

 trunks are occasionally almost hidden by the quantity 

 of fruit produced on them. One of the most beautiful 

 examples of this mode of flowering is a small tree of 

 the genus Polyaltliea, belonging to the family of the 

 custard-apples, not uncommon in the forests of North- 

 western Borneo. Its slender trunk, about fifteen or 

 twenty feet high, was completely covered with star- 

 shaped flowers, three inches across and of a rich orange- 

 red colour, making the trees look as if they had been 

 artificially decorated with brilliant garlands. The recent 

 discoveries as to the important part played by insects 

 in the fertilization of flowers offers a very probable 

 explanation of this peculiarity. Bees and butterflies 

 are the greatest flower-haunters. The former love the 

 sun and frequent open grounds or the flowery tops of 

 the lofty forest-trees fully exposed to the sun and air. 

 The forest shades are frequented by thousands of 

 butterflies, but these mostly keep near the ground, 

 where they have a free passage among the tree-trunks 

 and visit the flowering shrubs and herbaceous plants. 

 To attract these it is necessary that flowers should be 

 low down and conspicuous. If they grew in the usual 

 way on the tops of these smaller trees overshadowed by 

 the dense canopy above them they would be out of 

 sight of both groups of insects, but being placed openly 

 on the stems, and in the greatest profusion, they cannot 

 fail to attract the attention of the wandering butterflies. 

 Uses of Equatorial Forest-trees. Amid this immense 

 variety of trees, the natives have found out such as are 



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